Various implantable drug delivery devices are known in the art. For example, U.S. Patent Application Publication No. 2007/0202151 to Lee et al. and U.S. Patent Application Publication No. 2009/0149833 to Cima et al. describe drug delivery devices for minimally invasive deployment and retention in a cavity or lumen in a patient, such as the bladder. The devices resist excretion, such as in response to the forces associated with urination. For example, the devices may include a retention frame, which may be configured into a relatively low profile for deployment into the body, and once implanted may assume a relatively expanded profile to facilitate retention. The devices may provide controlled release of drug over an extended period in a predefined manner. In some embodiments, the devices include a water-permeable tube that defines a drug reservoir for housing a drug and at least one aperture for releasing the drug. Osmotic pumping or diffusion may be the dominant mechanism by which the drug is released from the reservoir. Highly water-soluble drugs, such as lidocaine hydrochloride, may be released via osmotic pressure at therapeutically useful rates over an extended period. In other embodiments, the device may be configured to release lower solubility or other drugs primarily or exclusively via diffusion.
It would be desirable, however, to provide improved drug delivery devices and systems. For example, it would be desirable to provide devices, systems, and methods in which relatively lower solubility drugs can be released at therapeutically useful rates by an osmotic pressure means over an extended period. It would also be desirable to provide implantable drug delivery devices and systems capable of delivering a variety of active agents at a selected release kinetics profile and to provide additional techniques, structures, and/or formulations to enhance control of drug release in vivo, for example from a device deployed in the bladder.